Australian football Hall of Famer Terry Wallace believes the competition could be about to flip on its head, with the three teams that were sitting atop the ladder only a month ago starting to lose their grip.

Geelong, Collingwood and GWS seemed to have separated themselves from the pack, but Richmond, West Coast and Brisbane have closed the gap and may even go passed them come Round 23.

“Three weeks ago, we were probably saying that three sides that you trusted the most were Geelong – they’ve lost two of their last three – Collingwood – they’ve lost their last two and GWS who have lost their last two,” Wallace told SEN’s Drive.

“It has flipped on its head, which has made it such an exciting season.”

Richmond is one of the teams who could make a charge at the top four, but Wallace wants to see them beat GWS this week before declaring them back in the hunt.

“When a game’s over in five minutes, you don’t take much out of it,” he said.

“But the players would be looking at each other and thinking we’re not far off it. We’re starting to mount something here.

“The confidence they got from that Grand Final victory a couple of years ago, it still stands strong with those premiership boys.

“We clearly need to see them play a decent side, though.”

Collingwood plays West Coast and the Tigers take on the Giants this weekend in two games that could define what the ladder looks like come the end of the season.